My son bought a lightly used truck(25,000 miles) and he's only getting 10mpg on the highway (physical measured test not computer). It's still on warranty and the dealer won't look at it. Any ideas where to start? I've had a lot of pickups in that class and they all got 20 on the highway at 60mph. This one is half!
2012 silverado with 5.3 litre getting 10 highway mpg
